opponents of egyptian president mohammed morsi marched toward the presidential palace in cairo today after he rejected their demands. thousands of his islamists supporters vowed vengeance for two men killed in clashes this week. u.s. and russia are trying to get on the same page regarding syria. top diplomats today announce another effort stopping the bloodshed and getting rid of bashar assad. national security correspondent jennifer griffin tonight from the pentagon on what happens if diplomacy fai fails. >> rebel forces close in on the airport, the planners expect fighting in syria to intensify. u.s. officials are pessimistic they can resol t syrian conflict diplomatically, but seem certain that assad is losing his grip on power. >> every syrian must be included this process for a new and better future. future cannot include assad. >> military in meantime is actively planning should vit to intervene to assure assad's chemical weapons. hundreds of u.s. and nato troops will soon be heading to the turkish border with syria to operate patriot missile defense batteries. this summer ther